copysignf(3) - Linux man page

Name

copysign, copysignf, copysignl - copy sign of a number

#include <math.h>

double copysign(double x, double y);
float copysignf(float x, float y);
long double copysignl(long double x, long double y);

Link with -lm.

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

copysign(), copysignf(), copysignl():: _SVID_SOURCE || _BSD_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L;
or cc -std=c99

The copysign() functions return a value whose absolute value matches that of x, but whose sign bit matches that of y.

For example, copysign(42.0, -1.0) and copysign(-42.0, -1.0) both return -42.0.

On success, these functions return a value whose magnitude is taken from x and whose sign is taken from y.

If x is a NaN, a NaN with the sign bit of y is returned.

No errors occur.

C99, POSIX.1-2001. This function is defined in IEC 559 (and the appendix with recommended functions in IEEE 754/IEEE 854).

On architectures where the floating-point formats are not IEEE 754 compliant, the copysign() functions may treat a negative zero as positive.